1. Field of the Invention
This invention relates to apparatus for filling containers with a liquid, and more particularly, to a liquid filler apparatus using a single control valve having either a ball-type or a butterfly-type valve element.
2. Description of the Prior Art
For reasons of economy, it is desirable to automatically control the introduction of liquid into containers which may range in size from a few ounces to many gallons.
In order to accurately fill a container with liquid in the quickest and most efficient manner, it is the practice in the art to introduce liquid into that container at a relatively high filling rate. When a predetermined weight of liquid has been introduced into the container being filled, the remaining portion of the liquid is admitted to the container at a slower fill rate. For apparent reasons, the first filling rate is known in the art as "fast fill" while the second filling rate has been termed "dribble fill". Of course, when the desired weight of liquid has been introduced into the container the dribble fill is terminated.
The cut-off points wherein changeover from fast fill to dribble fill and the termination of dribble fill occur is usually governed by feedback control signals generated by a scale arrangement upon which the container is disposed. First and second cut-off weights each representative of a predetermined weight within the container are used as set points for the changeover from fast fill to dribble fill and for the termination of dribble fill, respectively.
In the prior art, introduction of liquid into a container at both a fast fill rate and a dribble fill rate may be achieved through the use of a parallel arrangement of valves for dispensing liquid into the container. This parallel valve arrangement is located in the flow path intermediate the source of liquid and the container. To achieve a fast fill rate, the valves in each of the two parallel branches are both opened. Dribble fill rate is achieved by closure of the valve in one of the branches. Usually, the valve left open during dribble fill passes a flow rate less than that passed through the valve disposed in the other of the parallel branches. To terminate filling of the container, the valve in the second parallel branch is closed.
It is possible to use a control valve having a low cv factor to control the introduction of liquid to the container. Yet another alternative is to use a specially designed two-stage valve with a high cv factor. Of course, the disadvantage with both of these last-mentioned alternatives is high cost.
The liquid is usually introduced into the container through an elongated conduit or "lance" which may extend into the interior of the container. In connection with the filling of containers with certain liquids, such as detergents, a certain precautionary technique, known as "subsurface fill" must be taken to avoid foaming of the liquid, to prevent generation of fumes and noxious odors, as well as to prevent ignition of the material by accumulated static charges.
To effect a subsurface fill of a container the conduit or lance is inserted into the volume of the container for a distance such that the emission end of the conduit is disposed just above the bottom of the container. The liquid is then introduced into the container at a dribble fill rate until there is a level of liquid disposed within the container such that the emission end of the lance lies below the surface of the liquid. At this point, the liquid may be introduced at a fast fill rate until the changeover cut-off weight (i.e., volume) is reached. At this point, the dribble flow rate is used to bring the volume of liquid introduced into the container to the desired weight.
Subsurface filling arrangements usually utilize a primary and a secondary valve. The primary valve is located at a point on the lance outside of the container. The secondary valve is connected in the fluid flow path adjacent the emission end of the lance. The secondary, or dribble fill control valve, is usually operated by a rod extending through the interior of the lance. The dribble fill valve is moved with respect to the emission end of the lance to define fast fill and dribble fill positions by an actuator connected to the rod. The dribble fill valve is also used to prevent drips.
When using a subsurface filling arrangement such as discussed above, it is necessary to provide some apparatus to withdraw the lance from the container as the level of liquid in the container rises. This is necessary in order to provide an accurate measurement of the weight of the liquid introduced into the container.
It is believed to be advantageous to provide a single flow control valve having either a ball-type or a butterfly-type valve element in a flow control relationship within the conduit or in a position controlling the rate of liquid passing through the conduit at a location on the filling arrangement which at all times remains external to the container being filled.
It is also believed of advantage to provide a control valve having an actuator in cooperative association with the valve elements and responsive to the control signals generated by the scale such that the imposition of actuating forces to the actuator varies the effective cross-section flow area through the conduit in accordance with the actuating force to thereby provide both fast fill and dribble fill liquid flows through the conduit.
It is believed to be advantageous to provide a liquid filling arrangement using a control valve element of the ball-type or butterfly-type in cooperative association with a pressure actuator to control the introduction of a liquid into a container at a fast fill rate and at a dribble fill rate. It is also believed advantageous to provide a liquid filling arrangement such that the lance or conduit need not be withdrawn as the liquid level within the container rises during the practice of subsurface filling techniques.